Question: Solve for $x$ and $y$ using substitution. ${-2x-4y = 10}$ ${y = 6x+4}$
Answer: Since $y$ has already been solved for, substitute $6x+4$ for $y$ in the first equation. ${-2x - 4}{(6x+4)}{= 10}$ Simplify and solve for $x$ $-2x-24x - 16 = 10$ $-26x-16 = 10$ $-26x-16{+16} = 10{+16}$ $-26x = 26$ $\dfrac{-26x}{{-26}} = \dfrac{26}{{-26}}$ ${x = -1}$ Now that you know ${x = -1}$ , plug it back into $\thinspace {y = 6x+4}\thinspace$ to find $y$ ${y = 6}{(-1)}{ + 4}$ $y = -6 + 4$ $y = -2$ You can also plug ${x = -1}$ into $\thinspace {-2x-4y = 10}\thinspace$ and get the same answer for $y$ : ${-2}{(-1)}{ - 4y = 10}$ ${y = -2}$